1. Field of the Invention
The present invention relates to an optical module and a method of producing the optical module.
2. Description of the Background Art
The published Japanese patent application Tokukai 2002-90587 describes a method of producing an optical module. According to this method of producing an optical module, ultraviolet/heat-curable resin is applied in the shape of the circumference of a circle onto a surface for bonding with a stem portion at the end portion of a housing that mounts an optical semiconductor device. In a temporary fixing step, after a lens and an optical semiconductor device are optically aligned and bonded with each other, ultraviolet rays are radiated from the outside of the stem portion to ultraviolet-cure the ultraviolet/heat-curable resin. In a complementary curing step, the ultraviolet/heat-curable resin is heated to heat-cure the ultraviolet-unirradiated portion. In a bonding-reinforcing step, after thermosetting resin is applied in the shape of the circumference of a circle such that it covers the ultraviolet/heat-curable resin along the circumferential face of the stem portion, the thermosetting resin is heated in an atmosphere to set it.
In the above-described optical module, after the resin is applied over the entire circumference of the bonding portion, optical alignment is performed. Because the center of the external shape of the optically aligned housing is not coincident with that of the optical device, the thickness of the resin applied to the circumference of the stem portion is not uniform. Under this condition, when the resin is irradiated with ultraviolet rays, the nonuniformity in the resin thickness and variations in the irradiated dose of the ultraviolet rays to the resin act together to render the curing condition nonuniform in terms of the position of the applied resin. This nonuniformity causes optical-axis deviation from the aligned position. In addition, at the time of the curing of the resin by the irradiation of ultraviolet rays, a jig is used to hold the stem portion and the housing. When the bonded stem portion and housing are removed from the jig, the residual stress produced in the resin during the curing operation is released. This released stress also produces optical-axis deviation from the aligned position.
As described above, the thermosetting resin is applied in the shape of the circumference of a circle such that it covers the ultraviolet/heat-curable resin. However, most part of the bonded face is already covered with the ultraviolet/heat curing resin. Therefore, the bonding strength cannot be improved notably by the application of the thermosetting resin.